Advancements in digital communication technologies have permitted the development and deployment of communication systems having increased communication capacities and additional communication features. Radio communication systems, such as cellular and cellular-like communication systems, are exemplary of communication systems that make increasing use of digital communication technologies and techniques. While early-generation, cellular communication systems used analog communication techniques, successor communication systems make increasing use of digital communication technologies. Earlier, successor systems provide digital communication capabilities and also utilize circuit-switched (CS) communications in which dedicated channels are used for at least some communication services. Newer, as well as proposed, successor systems provide for end-to-end, packet-based communication services.
Amongst the services provided by new-generation systems are IMS (IP multimedia subsystem) centralized services. These services include, e.g., call waiting, call hold, and call forwarding. IMS centralized services are typically controlled by SIP/XCAP-based protocols, but the bearer is typically run by way of a circuit-switched connection in which SIP (Session Initiation Protocol) is run all the way to a wireless device using either an IP network, e.g., GPRS (General Packet Radio Service), in conjunction with circuit-switched connections of a circuit switched network or by defining a SIP derivative over a circuit-switched signaling, such as USSD (Unstructured Supplementary Data Service), SMS, another transport protocol, etc.
Two manners are currently defined by which a wireless device sets-up and terminates service control signaling pursuant to an IMS centralized service (ICS). The first manner is by way of a Gm interface. For a wireless device to be able to utilize the Gm interface, the wireless device must be DTM (Dual Transfer Mode), GPRS, and SIP capable. And, the other currently-defined manner is for the wireless device to utilize an Il reference point, proposed to use USSD but could be but not limited to SMS etc. The Il reference point is specified to cater to specific situations, such as when the wireless device does not have GPRS service, the network is not DTM capable, etc. In the context used herein, DTM means that the UE has the capability to perform both Circuit Switched (CS) and Packet Switched (PS) type operations in a simultaneous or near simultaneous manner. One example comprises DTM capability in a GERAN network. As those skilled in the art know, there are many other manners in which this could be achieved, such as, but not limited to, those capabilities of UTRAN or a multi radio device that is able to transmit and receive on multi radios. However, if the network is not DTM capable, mid call supplementary service operations cannot be performed. As an example, if the wireless device is in a session on a UTRAN network and another session is on hold and the wireless then moves, i.e., is handed off to, a GERAN network and, as a result, the wireless device is no longer able to retrieve the session that is on hold as DTM is not available. One existing solution, when DTM is not available, is for the wireless device to decide not to register with the IMS home network. The IMS network knows that the wireless device is reachable only by way of circuit-switched connections and that SIP is not available. However, in the event that the wireless device is to carry out other IMS services, such as PoC, OMA, SIMPLE, or other services, the wireless device must register with the IMS home network. When these, or other IMS services are to be used, therefore, not registering is not a viable solution. If the wireless device has to register with the home IMS because of other services, the IMS home network will not be aware that the wireless device is not in an area that is DTM capable, and the IMS home network attempts to set-up calls using IMS services. Call operations will not work.
Additionally, in conventional operation, a problem also is exhibited in the event that the wireless device loses packet access needed to control the IMS centralized services. And, when a Gm interface is not available, only Il is available. No protocol is presently defined for use of the Il reference point, particularly for mid-session services.
Existing communication system operation as it relates to IMS centralized services exhibits various problems that might interfere with, or prevent, the performance of an IMS, or other DTM, service.
An improved set-up and service termination control signaling for IMS centralized services is therefore needed.
It is in light of this background information related to radio communications that the significant improvements of the present disclosure have evolved.